The Second International became ineffective in 1916 during World War I because the separate national parties that composed the International did not maintain a unified front against the war, instead generally supporting their respective nations' role. The Secretary General of the ISB, Camille Huysmans, moved the ISB from German-occupied Brussels to The Hague in December 1914 and attempted to coordinate socialist parties from the warring states to at least July 1916.[4]French Section of the Workers' International (SFIO) leader Jean Jaurès's assassination, a few days before the beginning of the war, symbolized the failure of the antimilitarist doctrine of the Second International. At the Zimmerwald Conference in 1915, anti-war socialists attempted to maintain international unity against the social patriotism of the social democratic leaders.

In July 1920 at Geneva, the last congress of the Second International was held, following its functional collapse during the war. However, some European socialist parties refused to join the reorganized International and decided instead to form the International Working Union of Socialist Parties (IWUSP) (Second and a half International or Two-and-a-half International), heavily influenced by Austromarxism. In 1923, IWUSP and the Second International merged to form the social democratic Labour and Socialist International which continued to exist until 1940. After World War II, a new Socialist International was formed to continue the policies of the Labour and Socialist International and it continues to this day.

Latin America

The exclusion of anarchists

Anarchists tended to be excluded from the Second International, nevertheless "anarchism had in fact dominated the London Congress of the Second International".[6] This exclusion received the criticism from anti-authoritarian socialists present at the meetings.[7] It has been argued that at some point the Second International turned "into a battleground over the issue of libertarian versus authoritarian socialism. Not only did they effectively present themselves as champions of minority rights, they also provoked the German Marxists into demonstrating a dictatorial intolerance which was a factor in preventing the British labor movement from following the Marxist direction indicated by such leaders as Henry Hyndman.[8]